By adjusting the first cams relative to the second cams, the valves of a motor vehicle engine can be variably controlled. Thus, for example, the ratio between the intake timing and the exhaust timing can be modified as a function of load and rotary speed, if the intake valves on the one hand and the exhaust valves on the other hand are actuated by different groups of cams that can be adjusted relative to each other.
In order to enable a precise positioning of the cams and at the same time easy adjustability of the inner shaft relative to the outer shaft, the two shafts have to be supported in a suitable manner for rotation relative to each other. Thus, it is known in a generic camshaft having the above-described features according to DE 39 43 426 to provide sleeve bearings to support the ends of the shaft elements inside each other. This has the disadvantage that the sleeve bearings have to be fitted highly accurately in order to avoid play on the one hand and to ensure easy rotation on the other hand. The inner diameter of the outer shaft as well as the outer diameter of the inner shaft must be machined with high accuracy, but the processing of the internal surfaces of the outer shaft can be only done with a high level of processing complexity. A similar bearing concept is known from EP 1 963 625 [U.S. Pat. No. 7,802,549], where an end securing element connected to the inner shaft is supported radially on an inner surface of the outer shaft.